As is well known, it is typical in a gas turbine engine to include struts in an annular type of diffuser for transmitting a load across the gas path, and providing passageway means for carrying oil and other engine service lines. Such diffusers are conventionally utilized to diffuse the compressor discharge air so as to convert the dynamic pressure to static pressure prior to being admitted into the burner. While there are present designs that disclose that the number of fuel nozzles in the head of the burner are some integer number relationship to the number of struts, such designs conventionally include more fuel nozzles than there are struts. Further, although the struts of heretofore designs considered the aerodynamics and structural integrity, the accepted practice never took into consideration the expansion of the flow in the circumferential direction.
In the heretofore designs, the trailing edge of the struts in the prediffuser were fabricated into a blunt edge, but spaced relatively far apart. Hence, a given design would typically include less struts than there were fuel nozzles and its attendant air passages. This inherently created uneven flow characteristics of the air discharging from the prediffuser into the dump diffuser.
I have found that by equalizing the number of struts to the number of fuel nozzles and centering the fuel nozzles relative to the passageways between struts, the flow characteristics are enhanced. This is occasioned by the fact that the circumferential blockage is increased whereby the radial dimension in the diffuser passage can accommodate an increased dimension so that the mixing of the flow discharging therefrom is more rapid than would otherwise be in heretofore designs. This has the characteristics of reducing or minimizing wakes and flow distortions and hence delivering a more uniform flow pattern to the burner, thus minimizing localized hot spots on the burner walls.